This invention pertains to microwave systems and, more particularly, is concerned with arrays of microwave mixers.
One use of microwave mixers is conversion of signals at microwave frequency to an intermediate frequency, which usually is the difference between the frequency of the signal and that of a local oscillator. A plurality of mixers are sometimes arranged in an array which functions at a transmitting or receiving antenna.
The conventional method for distributing a local oscillator (LO) signal to many mixers uses a network of power dividers. In array antenna applications, the power divider network often must distribute the LO energy to hundreds or thousands of mixers. Power loss, weight, phasing, and space all become important considerations. The loss of power dividers required to feed many mixers dictate the need for a high-power local oscillator.
Another method to provide local oscillator power is to integrate an injection locked oscillator (ILO) with each mixer, each which is phase-locked to a common reference signal.
Both of these methods suffer from two problems particularly at millimeter wave frequencies. First, both are very costly, the ILO system being the more expensive of the two. Second, in constrained space applications such as exist in millimeter wave array antennas, it is often not physically feasible to use either of these methods.
An objective of the invention is to distribute a common LO signal to a plurality of mixers such as those in an array antenna without the losses associated with power divider networks.